With Windows Phone 8.1, Microsoft reworked its mobile operating system into something more modular, making it far easier to update elements that, previously, were deeply integrated into the OS. Components like the Xbox Music and Games hubs were disentangled from the core OS, and reestablished as apps that could be improved more regularly than the infrequent OS updates.

Calendar is another example of this modular app-based approach to OS features, and the latest update to the Calendar app for Windows Phone 8.1 was pushed to devices in the last few hours. Unfortunately, this update has introduced a serious bug which renders the app unusable for many.

As noted tech journalist Simon Bisson noted today, the Calendar app now crashes as soon as you try to create a new appointment:

Hmm. Looks like the update to the Windows Phone 8.1 Preview Calendar broke something. Crashes when you try to create a new appointment.

We have tested the Calendar app on a range of devices running Windows Phone 8.1 Preview for Developers, and on the Lumia 630 with Windows Phone 8.1 and Lumia Cyan firmware. On each of these devices, the same thing happened every time we tried to open or edit an appointment - the app simply crashed and threw us back to the Start screen.

The Windows Phone support team are aware of the problem - in a response to developer and blogger Shawn Wildermuth, @WinPhoneSupport told him that they are working on a resolution, but did not elaborate further:

@ShawnWildermuth Sorry for the troubles that may have caused. We are aware of that and we are working on it.

Until Microsoft sorts this issue out, though, there is one workaround that you can use in the meantime: Cortana. We've tested creating, editing and deleting appointments in the Calendar using Cortana voice interactions, and all of these functions can be performed without issue.

While this solution is not exactly ideal for those more accustomed to making quick text edits to their Calendar appointments, it's better than nothing until Microsoft resolves the problem.